Lubricant



Patented Oct. 10, 1933 PATENT OFFICE LUBRICANT Roy F. Nelson, Port Arthur, Tex., assignor to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application December 13, 1930 Serial No. 502,256

12 Claims.

This invention relates to lubricants, and more particularly to cutting oils used for drilling, thread cutting and similar lathe machinework.

The use of cutting oils in ordinary operations of machine shops is well known. The function of the cutting fluid is usually two-fold; that is, as a cooling agent to keep the drilling or cutting tools from over-heating, and as a lubricant to alleviate friction between the contacting parts.

0 The requirement of a good cutting fluid is, therefore, that it provide a certain degree of cooling, and espec ally that it have suificient oiliness to adhere to the working parts and reduce the friction to a minimum. Sometimes it is necessary to cool the working parts with water or similar fluid having a high specific heat. In the latter practice, it is desirable that the lubricant will not wash from the metal surfaces and often preferable that it form an emulsion with the cooling agent. Straight mineral oils, are ordinarily good lubricants, but they are not entirely satisfactory as cutting oils. Other sources have, accordingly, been sought, or the mineral oils have been treated to transform them, into satisfactory lubricants for this purpose.

Various methods of treating mineral oils to produce satisfactory cutting oils have been employed heretofore. Certain animal oils, such as lard oil, because of their oiliness have been blended with mineral oil to confer greater efiiciency on the lubricant. The quantity of lard oil required is usually quite large, thereby making the cutting oil somewhat expensive. Emulsifying agents such as soaps have sometimes been added to mineral oil to produce a cutting oil which will have increased oiliness, and more especially to confer on the oil the property of emulsifying with the cooling fluid which may be added. In this way, instead of the oil entirely washing away when a cooling agent is applied, an emulsion is formed which contains sufiicient oil to provide a certain degree of lubrication. Sulphurized oils compr sing vegetable oils or mineral oils, with limited quantities of sulphur incorporated therein, have also been used to advantage to increase the viscosity, oiliness and emulsifying properties of cutting o ls. The efiiciency of the latter type of oils has very largely depended on the sulphur content, which has been somewhat limited due to the low solubility of sulphur in the oil and the inability to incorporate large quantities there n.

The present invention has to do with an im proved sulphurized mineral cutting oil prepared in a novel manner and having a particularly high sulphur content. Cutting oils comprising minera1 oil, sulphur and a sulphur solvent are old in the art and no claim is made, broadly, to such a product, but, as far as I am aware, no cutting oil containing the high percentage of sulphur of my product'has been successfully prepared prior to the invention. Furthermore, incorporation of sulphur into mineral oils to prepare-cutting oils is recognized as old in the art, but all the prior methods, to the best of my knowledge, have involved treating the oil in the presence of free sulphur, at various temperatures, under atmos-. pheric pressure. One of the important features of. my process that is considered novel and which has produced unexpected results, resides in the incorporation of the sulphur into the oil under substantial superatmospheric pressure.

More particularly, according to the invention,

a mineral oil, preferably having a viscosity of at least or exceeding 70 seconds Saybolt at 100 R,

is mixed with sulphur and .the mixture heated under pressure to a temperature in excess of 300 F., preferably 350 F. to 450 F. The pressure may be applied from an extraneous source, but it is usually more convenient to allow the mixture to build up a self-generated pressure by the evoso lution of reaction gases, such as hydrogen sulphide. A pressure of about 75 to 150 lbs. per-sq. in. is preferable, although best results have been obtained with a pressure of approximately 100 lbs. per sq. in. The amount of sulphur retained by the oil has been found to increase with the time the mixture is digested or held under the operating conditions of temperature and pressure. The time varies somewhat with the character of the oil, and the degree of sulphurization 9O desired; however, a period of 2 to 10 hours has been found satisfactory in most instances. The viscosity of the oil is usually increased considerably by the incorporation of sulphur therein. This increase may range from 25 to 100 seconds Saybolt or more. It is preferable that the finished product have a viscosity in excess of 75 seconds Saybolt at F.

The reaction between the sulphur and oil has been found to liberate large quantities of re- 100 action gases, such as hydrogen sulphide, which normally escape but under pressure either combine with or remain dissolved in the oil after the pressure is released. The latter is particularly true when the reaction period provides insufiieient time-for complete absorption of the sulphur by the oil. The hydrogen sulphide imparts a disagreeable odor if allowed to remain in the finished product. It is preferable, therefore, to remove the dissolved gases as completely as possible. This may be done by applying a vacuum to the oil to draw out the dissolved gases or to blow a stream of gas, such as air, through the oil to carry out the hydrogen sulphide. It may be desirable in some cases to mix substances with the mineral oil and sulphur mixture, which will absorb or destroy any foul gases. Sulphur dioxide has been suggested for this purpose. Furthermore, it may sometimes be advantageous to add materials which not only are capable of absorbing sulphur and destroying the foul odor of the sulphur containing gases, but also will give a positive and more pleasant odor to the finished product. Pine tar has been used with this object in view.

Oils prepared in accordance with the invention are characterized by their high sulphur content. For example, a pale oil with the viscosity of about '77 seconds Saybolt at 100 F. heated with sulphur for 10 hours at about 390 F. and under a pressure of approximately 100 lbs. per sq. produced a finished oil containing'6.8'7% sulphur and a viscosity of 136 seconds Saybolt at 100 F. A light paraffin distillate with a viscosity of 86 seconds Saybolt at 100 F., treated by substantially the same procedure, produced a cutting oil having 8.6% sulphur and a viscosity of 106 seconds. Saybolt at'100 F. Other products containing sulphur in quantities ranging from 4% to 10% maybe easily prepared. From 2% to 10% sulphur absorbing material, such as pine tar, may be added to the above product if desired.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may

be made without departing from the spirit and y scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of treating mineral oils to produce cutting fluids, which comprises mixing sulphur with an oil having a viscosity of at least '70 seconds Saybolt at 100 F. and heating the mixture to a temperature at which reaction between the oil and sulphur occurs while maintaining the reacting materials under a superatmospheric pressure of about '75 lbs. to 150 lbs. per sq. in.

2. A process substantially as described in claim 1 in which the superatmospheric pressure is selfgenerated by confining vapors and gases evolved during the heating operation.

8. A process substantially as described inclaim 1 in which the temperature is 350 F. to 450 F.

-of the pressure, by

4. The method of treating mineraloils to produce cutting fluids, which comprises heating a mixture of mineral oil and'sulphur to a temperature of about 400 F. and at a pressure of about 100 lbs. per sq. in. for a period of time suflicient to incorporate in said oil a substantial amount of sulphur.

5. A method substantially as described in claim 4 in which the time under pressure is 2 to 10 hours.

6. The method substantially as described in claim 4 in which the amount of sulphur incorporated is 4% to 10% of the weight of the oil.

'7. The method of preparing sulfur cutting oils which comprises digesting a viscous hydrocarbon oil in the presence of free sulfur at a temperature in excess of 300 F. and .under a superatmospheric pressure of about '75 lbs. to 150 lbs. per sq. in.

8. In the preparation of sulfurized cutting oils wherein sulfur is incorporated in an oil of viscosity of at least '70 seconds Saybolt at 100 F. under the influence of heat, the improvement which comprises maintaining a superatmospheric pressure of at least '75 lbs. per sq. in. on the oil during the sulfurizing operation.

9. The method which comprises incorporating sulfur into a lubricating oil while maintaining the oil at an elevated temperature and under a pressure in excessof '75 lbs. per sq. in.

10., The method of sulfurizing oils which comprises subjecting a hydrocarbon oil having 'a viscosityv of at least '70 seconds Saybolt at 100 F. to the action of sulfur at a temperature in excess of 300 F. and under a superatmospheric pressure of at least '75 lbs. per sq. in.

11. In the manufacture of sulfurized oils wherein sulfur is incorporated into a hydrocarbon oil while maintaining the 6 under substantial superatmospheric pressure and'at a temperature sufiiciently high to efiect reaction between the sulfur and the oil, the step of removing gases, of disagreeable odor, which are liberated and would partially remain in the finished oil after release blowing the finished oil with a stream of gas to carry out the undesirable gases.

12. A mineral oil product consisting essentially of a parafiinic lubricating oil of at least '70 seconds Saybolt viscosity at 100 F. containing about 4% to 10% by weight of sulfur and resulting from the heating of the oil with sulfur under substantial superatmospheric pressure.

ROY F. NELSON. 

